Method for compensating earth surface temperatures for the skyward effect thereon

ABSTRACT

A method for compensating measured earth surface temperatures for the effects which skyward temperatures have upon such measured temperatures. Also, methods for employing compensated earth surface temperatures to determine the likelihood of subsurface features existing beneath locations within a selected geographical area.

This application is a division of U.S. Ser. No. 08/668,814, filed Jun.24, 1996, now U.S. Pat. No. 5.743,642.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for compensating measured earthsurface temperatures for the effect of skyward conditions upon suchtemperatures. More particularly, the present invention relates tomethods for using temperatures measured in a skyward direction forcompensating measured temperatures of the earth's surface. The earthsurface temperatures compensated according to the method of the presentinvention are useful for determining subsurface features, such as thepresence or absence of oil, gas, or mineral deposits.

2. Description of Pertinent Art

It has been known since at least the Middle Ages that the earth'ssurface at locations above mineral deposits, such as metal ores, iswarmer than the earth's surface above locations where such mineraldeposits do not occur. Early reports describe the selective melting offrost at locations above mineral deposits, while the frost at otherlocations, where no mineral deposits were found, remained unmelted.

In U.S. Pat. No. 4,476,716 (Fons), incorporated by reference into thisapplication in its entirety, I disclosed methods for predicting thelikelihood that oil or gas deposits are present at unexplored depthsbelow selected locations on the earths surface. These methods were basedupon the discovery that the temperature of the earth at a given depthbelow a location above an oil or gas deposit tends to be lower thantemperatures at the same depth at other locations in the same geographicarea where oil or gas deposits do not exist.

One method taught in U.S. Pat. No. 4,476,716 for predicting thelikelihood of an oil or gas deposit below a location comprises:determining a first temperature (Tq) at a first known depth beneath aselected location; determining a second temperature, (Tr.),representative of the average temperature for the first known depthwithin a geographic area within which the location is situated; anddetermining a temperature difference, ΔT=Tq-Tr., where, for a negativevalue of ΔT, it is likely that an oil or gas deposit is present beneaththe location. As exemplified by claims 11 and 12 of U.S. Pat. No.4,476,716, the method may be applied where the first known depth isabout the surface of the earth. The accuracy of predictions made usingthese methods are dependent upon the accuracy of temperature data at thelocations under study. At Col. 5, lines 14-18, of U.S. Pat. No.4,476,716 I stated, "Where surface and ambient temperatures are veryaccurately determined, temperature differences in the range of 1° F. maybe used to predict the presence of oil or gas deposits at selectedlocations." In U.S. Pat. No. 4,476,716 I disclose that accurate surfacetemperature data and atmospheric temperature may be obtained for somelocations in the form of annual average temperatures from Geological andMeteorological surveys.

In U.S. Pat. No. 5,524,483 (Fons), incorporated herein in its entiretyby reference, I disclose methods for predicting the likelihood of thepresence of oil or gas deposits beneath locations within a geographicarea on the earth's surface employing earth surface temperatures at thelocations. The methods disclosed in U.S. Pat. No. 5,524,483 comprisemeasuring earth surface temperatures at a plurality of points, (eachhaving similar surface features), during a time period during whichambient conditions, (for example: ambient temperatures, incidentradiation, degree of cloud cover, precipitation, wind and atmospherichumidity and clarity), are similar for minimizing the variability ofearth surface temperatures from point to point due to changes in suchambient conditions. Points having lower than average earth surfacetemperatures were identified as being more likely to have oil or gasdeposits beneath them than were other points having higher than averageearth surface temperatures.

In U.S. Pat. No. 5,281,024 (Fons), incorporated herein in its entirety,I disclose methods for locating deposits of soil having high percolationrates in areas having both permeable and impermeable soils employingearth surface temperature measurements. According to the methods of U.S.Pat. No. 5,281,024, locations having higher earth surface temperaturesare more likely to have permeable soils present than are locations inthe same area having higher earth surface temperatures.

Earth surface temperatures are affected not only by seasonal changes intemperature, but also by more immediate factors, such as diurnaleffects, variation in topographical features, including soil type, soilmoisture, reflectance/emissivity of the earth's surface, vegetativecover, elevation above/below sea level, grade and other surface featuresas well as changes in ambient conditions such as incident radiation(sunlight), ambient temperatures, atmospheric humidity, winddesiccation, cloud cover, atmospheric clarity, and precipitation,. Thesefactors tend to create variations in measured earth surface temperatureswhich mask any temperature differences between two or more locationsarising from the presence or absence of oil or gas deposits, or of othersubsurface features beneath the locations. While time averages, such asaverage annual earth surface temperatures as disclosed in U.S. Pat. No.4,476,716, tend to eliminate the masking effect of these factors suchthat earth surface temperatures differences due to the presence orabsence of oil or gas deposits or other subsurface features can beobserved, obtaining such time average temperature data is noteconomically or functionally practical. Selecting a time period duringwhich these factors change little, as disclosed in U.S. Pat. No.5,524,483, allows collection of earth surface temperature data which isuseful for determining subsurface features. However, as will be seenbelow, ambient conditions tend to change, and thus corrupt the earthsurface temperature data collected, even during short time periods.

A practical method for acquiring earth surface temperature datarelatively unaffected by the above factors, especially changes inambient conditions, and which is useful for determining the presence orabsence of subsurface features, such as oil, gas or mineral deposits, isdesirable

SUMMARY OF THE INVENTION

Now, according to the method of the present invention, I have discoveredimproved methods for acquiring earth surface temperature data which isuseful for determining the presence or absence of subsurface features,such as oil, gas, or mineral deposits, beneath selected earth surfacelocations, and improved methods for selecting locations suitable forexploring for oil, gas, or mineral deposits.

The present invention is based upon my discovery that earth surfacetemperatures at locations are significantly affected by ambientconditions in a skyward direction above such locations. Changes in suchambient conditions have a rapid and significant effect upon measuredvalues of earth surface temperatures at the locations and tend to masktemperature differences between locations which would indicate thepresence or absence of subsurface features, such as oil, gas or mineraldeposits at such locations.

In one embodiment, the present invention comprises:

a) Selecting an area of interest upon the earth's surface;

b) Measuring an earth surface temperature, T_(L), at each location of aplurality of locations within the selected area and simultaneouslymeasuring a skyward temperature, T_(S), in a vertical direction aboveeach of the locations;

c) Determining the average temperature, T_(SA), of the skywardtemperatures, T_(S), measured above each location;

d) Determining a normalized temperature, T_(NS), for each skywardtemperature according to the formula: T_(NS) =T_(SA) -T_(S) ; and

f) Determining for each location a compensated earth surfacetemperature, T_(CL), according to the formula: T_(CL) =T_(L)-(C)(T_(NS)),

where C is a constant proportional to the effect of skyward temperatureupon the measured earth surface temperature, T_(L). By following themethod of the above embodiment of the invention, earth surfacetemperatures compensated for the effect of skyward ambient conditionsmay be obtained for a plurality of locations, which compensated earthsurface temperatures, T_(CL) may then be compared for determining whichlocations among the plurality of locations might have desirable subsurface features. An average, T_(CLA) of all the compensated earthsurface temperatures, T_(CL) is determined. Then, in an area wheremineral deposits are likely, locations in the area having values ofT_(CL) higher than average compensated earth surface temperature T_(CLA)rare more likely to have mineral deposits beneath them than arelocations in the area having values of T_(CL) lower than averagecompensated earth surface temperature T_(CLA). Similarly, in an areawhere oil or gas deposits are likely, locations in the area havingvalues of T_(CL) lower than average compensated earth surfacetemperature T_(CLA) are more likely to have oil or gas deposits beneaththem than are locations in the area having values of T_(CL) higher thanaverage compensated earth surface temperature T_(CLA).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings shows graphical plots of measured earth surfacetemperatures at locations along Traverse 1 and Traverse 2 of Example 1.

FIG. 2 of the drawings shows graphical plots of normalized compensatedearth surface temperatures for locations along Traverse 1 and Traverse 2of Example 1.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

As noted above, measured earth surface temperature values are affectedby ambient conditions, such as incident radiation(sunlight), ambienttemperatures, atmospheric humidity, wind dessication, cloud cover,atmospheric clarity, precipitation, etc. I have discovered that theseambient conditions are subject to rapid changes, even when, to a visualobserver, the ambient conditions appear stable. Further, I havediscovered that such changes in ambient conditions have significanteffects upon earth surface temperature measurements which can maskdifferences in earth surface temperature measurements between locationswhich differences could indicate the presence or absence of subsurfacefeatures at the locations.

According to the present invention, I have discovered that measuredearth surface temperatures can be compensated for changes in ambientconditions employing skyward temperatures, as described above in theSummary Of Invention. Differences in compensated earth surfacetemperatures between locations can then be compared to determine whethersought for subsurface features may exist below one or another of thelocations.

In geographical areas where oil or gas deposits are likely to be found,locations having lower compensated earth surface temperatures are morelikely to have oil or gas deposits beneath them than are other locationsin the same geographical area having higher compensated earth surfacetemperatures. Likewise, in geographical areas where mineral deposits,such as metal ores, are likely to be found, locations having highercompensated earth surface temperatures are more likely to have mineraldeposits beneath them than are locations having lower compensated earthsurface temperatures.

Factors other than ambient conditions and subsurface features can affectmeasured earth surface temperatures. For example, seasonal climaticchanges, and differences in earth surface features such as soil type,reflectance/emmissivity of the surface, vegetative cover, elevationabove or below sea level and other topographical features also canaffect the values of measured earth surface temperatures. As set out inU.S. Pat. No. 5,524,483, steps may be taken for reducing the effect ofthese other factors upon measured earth surface temperatures. Forexample, earth surface temperatures may be measured at locations withina geographical area during a period when seasonal climatic changes, frombeginning to end of the period, are not substantial.

The effect of differences in topographical features upon earth surfacetemperatures measured at locations within a geographical area may bereduced by selecting locations having similar topographical features.Visual inspection of locations for similarity of topographical featuresis generally sufficient. Roads, paved and unpaved, and bar ditches oftenprovide extensive areas having similar topographical features and can beused to advantage as locations for measuring earth surface temperatures.

Heat is continuously exchanged between the earth's surface, thesuperposed atmosphere and extra terrestrial entities, such as the sunand space. A substantial portion of this heat exchange is accomplishedby radiation. That is, heat is continuously radiated from the earth intothe atmosphere and, in clear weather, into space. Additionally, heat iscontinuously radiated from the atmosphere, from space and, when present,from the sun to the earth's surface. The net radiative heat transfer,either to or from the earth's surface, has a substantial effect upon themeasured value of the earth's surface temperature.

This effect of radiative heat transfer upon measured earth surfacetemperatures is well known and widely observed. For instance, cloudcover during the day tends to reduce earth surface temperatures,compared with temperatures measured in clear conditions, because theclouds prevent heat radiation from the sun reaching the earth's surface.The same cloud cover at night, however, tends to increase the earth'ssurface temperature, again compared to clear conditions, because theclouds prevent heat from the earth radiating into space. Also, it isknown that moisture content of the atmosphere affects radiation to andfrom the earth's surface because the water comprising the moistureabsorbs infra-red radiation.

In addition to the observable ambient conditions, such as presence orabsence of the sun or of clouds, relative humidity, etc., I havediscovered that conditions in a skyward direction above a location onthe earth's surface are subject to more subtle effects which can changerapidly and which have a significant effect upon the measured value ofthe earth's surface temperature at the location. I have also discoveredthat such changes in skyward conditions above a location can be sensedand quantified as changes in temperature measured in a skyward directionabove the location. Additionally, I have discovered that such changes inskyward conditions have a rapid and substantial effect upon earthsurface temperatures measured at the location. The effect of the changesin skyward conditions upon measured earth surface temperatures atlocations in a geographical area can mask differences in earth surfacetemperatures between locations which would indicate the presence orabsence of sub surface features beneath the locations.

According to the present invention, I have discovered methods forcompensating measured earth surface temperatures for such changes inskyward conditions such that the compensated earth surface temperaturesare more useful for predicting the presence or absence of sought for subsurface features.

In a preferred embodiment, the method of the present inventioncomprises:

selecting a geographic area beneath which desirable subsurface featuresmight be found;

selecting a plurality of locations throughout the geographic area havingsimilar topographical features, for reducing the variability of earthsurface temperatures among the locations;

measuring an earth surface temperature, T_(L), for each location of theplurality of locations and simultaneously measuring a skywardtemperature, T_(S), above each location of the plurality of locations;

determining a normalized temperature, T_(NL), for each location of theplurality of locations according to the formula

    T.sub.NL =T.sub.L -T.sub.LA

where T_(LA) is the average of all the earth surface temperatures,T_(L), for the plurality of locations;

determining a normalized temperature, T_(NS), for each skywardtemperature above a location of the plurality of locations according tothe formula

    T.sub.NS =T.sub.SA -T.sub.S

where T_(SA) is the average of all the skyward temperatures, T_(S),above the plurality of locations;

determining a compensated normalized temperature, T_(NCL) for eachlocation of the plurality of locations according to the formula

    T.sub.NCL =T.sub.NL -(C)(T.sub.NS)

where C is a constant proportional to the effect of skyward temperature,T_(S), upon the measured earth surface temperature, T_(L), at eachlocation of the plurality of locations. The constant C may beexperimentally determined, as follows: At a location, L, determining afirst normalized earth surface temperature T_(NL-1) and a firstnormalized skyward temperature T_(NS-1) at a first time t₁ ; determininga second normalized earth surface temperature, T_(NL-2) and a secondnormalized skyward temperature T_(NS-2) at a second time t₂ ; andcalculating a value for C according to the equation

    C=(T.sub.NL-1 -T.sub.NL-2)/(T.sub.NS-2 -T.sub.NS-1).

The earths surface is, over the course of a day, generally undergoingeither a process of heating or cooling due primarily to the effects ofdiurnal changes. That is, as the day closes and the amount of radiationreceived from the sun declines, the earth's surface begins to cool. Thiscooling effect extends into the night as heat from the earth is radiatedinto the sky. Later, as morning approaches, the earth's surface beginsto heat in response to the returning sun. This heating continues duringthe day until evening approaches and radiation from the sun againdecreases. Occasionally, the diurnal effect upon the earth's surfacetemperature is masked, as by heavy cloud cover, by precipitation or byother weather changes. These diurnal changes and weather changes canalso affect skyward temperatures measured according to the above method.When diurnal changes and weather changes are having an effect upon earthsurface temperatures or skyward temperatures, such effects of thediurnal changes and weather changes must be taken into account. That is,in the above method the measured earth surface and skyward temperaturesmust be adjusted for any significant temperature changes due to diurnalchanges and weather changes or, preferably, the earth surface andskyward temperature measurements will be made during a time periodduring which the diurnal and weather changes effects upon suchtemperature measurements are not significant. Generally, during timeperiods of from about 2 to 4 hours at about midday or late at night,earth surface and skyward temperature measurements can be made withoutsignificant effect by diurnal changes. For the case where diurnalchanges and weather changes do have a significant effect upon themeasured earth surface and/or skyward temperatures, the rates of changeof such measured temperatures due to diurnal changes and weather changesmay be determined by means well known in the art, and the measuredtemperatures may then be adjusted for the effect of the diurnal changesand weather changes.

The proportionality constant C indicates the effect of a change ofskyward temperature upon the associated measured earth surfacetemperature. That is, for a change, ΔTs, in skyward temperature above alocation, the measured earth surface temperature at the location willchange by an amount C(ΔTs). For situations where ambient conditions arerelatively steady during the time period when earth surface temperaturesand skyward temperatures are measured, a single value for C may be usedfor all calculations in the method above. For example, if thetemperature measurements are made at night under a clear sky, then asingle value for C may be used for all calculations. Likewise, iftemperature measurements are made at night and the sky has a solid cloudcover, then the same value of C may be used for all calculations.Similarly, if temperature measurements are made during the day and thesky is either clear or has a solid cloud cover during the entire periodduring which temperature measurements are being made, then the samevalue of C may be used for the calculations. The same value for C maynot be used for all calculations if skyward conditions are undergoing asubstantial change during the time period when temperature measurementsare being made, such as periods when radiation from the sun is causingrapid heating of the surface, or the earth's surface is undergoing rapidradiative cooling or periods when the weather is in a process of change,such as clearing or becoming cloudy. In such cases, it may be necessaryto determine a value for C for each skyward temperature measured.Preferably, measurements of the earth surface temperatures and skywardtemperatures for all locations are made during a time period duringwhich observable ambient conditions are stable and one value of C may beused for calculation of compensated earth surface temperatures, Tcl, forall locations.

The constant C may be experimentally determined. For example:

measuring, at a first time, a first earth surface temperature T_(L-1)and a first skyward temperature, T_(S-1) at a location;

measuring, at a second time, a second earth surface temperature T_(L-2)and a second skyward temperature, T_(S-2) at the same location; and

calculating a value for C according to the formula:

    C=(T.sub.L-1 -T.sub.L-2)/(T.sub.S-2 -T.sub.S-1)

This value for C may then be used to calculate compensated earth surfacetemperatures at the other locations within the geographical area.Preferably however, values for C are calculated, as above, for aplurality of locations within the geographical area where compensatedearth surface temperatures are desired. Then a single value of C isselected which gives the mathematical best fit for the value of C at allof the locations in the geographical area. By this preferred method, theeffect of any error which may be made in calculation of a value for Cany one location upon the compensated earth surface temperature valueswill be reduced.

Experience may indicate a value for C. For example, after manyexperiments in Southeast Texas, I have found that C of value 0.5 is agood first approximation for experimental runs where earth surface andskyward temperatures are measured during periods of visually clearweather at night, and such value can be used to calculate compensatedearth surface temperature values from temperature data collected undersimilar circumstances.

Compensated normalized earth surface temperatures, T_(NCL), determinedfor locations within a geographical area, according to the methods ofthe present invention, are useful for identifying locations havinghigher or lower than average earth surface temperatures, after skywardeffects are removed. Such compensated normalized earth surfacetemperatures, T_(NCL), are useful for identifying locations within ageographical area which are likely to have certain subsurface features.

For example, in a geographical area beneath which oil or gas depositsare likely to be found, then locations within the geographical areahaving compensated normalized earth surface temperatures, T_(NCL), ofnegative value are more likely to have oil or gas deposits beneath themthan are locations within the geographical area having compensatednormalized earth surface temperatures, T_(NCL), of positive value.Likewise, in geographical areas likely to have mineral deposits, such asmetal ores, locations in the geographical area having compensatednormalized earth surface temperatures of positive value are more likelyto have such mineral deposits beneath them than are locations havingcompensated normalized temperature values of negative value.

In the methods of the present invention, earth surface temperatures andskyward temperatures may be measured with any applicable temperaturemeasuring device which provides sufficient precision and reproducibilityof temperature measurement. Temperature measurements are preferably madeto a precision of about 1/4° F., (about 1/10° C.), or less. Compensatedtemperature differences of as little as 1/2° or less may be significantin determining whether sought for subsurface features are likely to befound beneath selected locations. Reproducibility of temperaturemeasurements is equally important as precision of the measuringinstrument. Preferably temperature measuring instruments employed inpractice of the present invention will have no substantial drift. Fortemperature measuring instruments which do have substantial drift, it ispreferable that the rate of such drift is known and that measuredtemperatures are corrected for such drift before being used in themethods of the present invention.

Temperature measuring instruments which contact the earth, such asthermometers and thermocouples, may be used to measure earth surfacetemperatures. Also remote sensing instruments, such as infra-redsensors, may be used to measure earth surface temperatures.

Remote sensing instruments, such as infra-red sensors, are required formeasuring skyward temperatures. The skyward temperature values areaffected by conditions in the lower atmosphere, the upper atmosphereand, where visible, space. The remote sensing instrument employed formeasuring skyward temperatures is preferably directed vertically upwardand is mounted at substantially the same elevation above the earth'ssurface as is the temperature sensor employed for measuring the earth'ssurface temperature. As demonstrated in Example 1 of U.S. Pat. No.5,281,024, near surface atmospheric conditions have a substantial effectupon measured temperature values and care should be taken to ensure thatskyward temperatures are measured for a skyward area substantiallyvertically above the earth's surface where earth surface temperaturesare measured.

Preferably, infra-red sensors are employed in the methods of the presentinvention for measuring both earth surface temperatures and skywardtemperatures. Also, infra-red sensors having heightened sensitive totemperatures in the ranges expected for earth surface temperatures andskyward temperatures are preferably employed Temperature measurementscan be made rapidly, with good precision, using infra-red sensors.Drift, or other lack of repeatability, in temperature readings obtainedwith infra-red sensors can be eliminated or compensated for by usinggood quality sensors and following the manufacturer's instructions.

For measuring earth surface temperatures with remote sensors, such asinfra-red sensors, it is preferable that the sensor be maintained atsubstantially the same distance, or elevation above and at an angle ofabout 90° to the earth's surface for minimizing the effect of theintervening atmosphere, between the sensor and earth's surface, upon themeasured temperatures. Atmospheric conditions, such as relativehumidity, moisture, fog, haze, and so on have a substantial effect uponthe temperature measured. This effect increases as the thickness of theatmosphere between the sensor and earth's surface increases. Preferably,the sensor is maintained at a distance above the earth's surface suchthat the conditions in the intervening atmosphere have no substantialeffect upon the value of the earth's surface temperature measured.Distances between the sensor and the earth's surface of about 1 to 3feet are preferred, although greater or lesser distances may be used ifconditions warrant.

Infra-red sensors have a field of view expressed by an angle of view.Infra-red sensors receive radiation emitted within their field of viewand thus record a temperature which as about average across the field ofview. Infra-red sensors having an angle of view in the range of about20-45 degrees sense the major portion of radiation from a skywarddirection which will strike the earth's surface at a location and are,thus, satisfactory for use in measuring both earth surface and skywardtemperatures.

EXAMPLE

The following example is provided to demonstrate the present invention.For this Example, a geographical area comprising the Katy Gas Field inSouth East Texas was selected. The Katy Gas Field is a known producingarea which has a known temperature profile against which the resultsfrom the method of the present invention can be compared.

Earth surface and skyward temperatures were measured using two OmegaEngineering Company OS-82-LT Infra-red Thermometers sensitive toradiation in the range of 8 to 14 Angstroms. Both infra-red thermometerswere mounted on the front bumper of an automobile about two feet abovethe road surface. The infra-red thermometer for measuring earth surfacetemperatures was directed vertically downward at the road surface, andthe infra-red thermometer for measuring skyward temperatures wasdirected vertically upward toward the sky. The terrain traversed wasessentially flat, such that the infra-red thermometers did not changetheir vertical orientations due to changes in grade.

The automobile traversed the selected geographical area along pavedhighways at about 60 miles per hour. Earth surface and a skywardtemperature measurements were made at locations at one-half mileintervals along each traverse.

In this Example, two traverses across the Katy Gas Field were made usingthe equipment and procedures described above. Both traverses were madeat night under visually clear weather conditions. The two traverses,(traverse 1 and traverse 2), were separated by a time period of abouttwo hours. Each traverse took about 27 minutes to complete. Data fromthe two traverses are shown in Table I.

Measured earth surface temperatures from traverse 1 are recorded inTable 1, column entitled "Traverse1, Earth Surface Temp" and are plottedas curve 10 in FIG. 1 of the drawings. Likewise, measured earth surfacetemperatures from traverse 2 are recorded in Table 1, column "Traverse2, Earth surface Temp" and are plotted as curve 11 in FIG, 1 of thedrawings.

As can be seen in FIG. 1, the measured earth surface temperatures fromtraverse 1 and 2 do not correspond well. At most locations, substantialdifferences exist between earth surface temperatures measured duringtraverse 1 and traverse 2. Additionally, the general shapes of curves 10and 11 do not correspond. One could not gain any information concerningthe presence or absence of subsurface features at any location from aninspection of curves 10 and 11.

According to my discoveries, variations in skyward temperatures above alocation have a significant effect upon earth surface temperaturesmeasured at the location. And, according to the present invention,measured earth surface temperatures can be compensated for suchvariations in skyward temperatures. The compensated earth surfacetemperatures can then be used to determine the likelihood of theexistence of subsurface features beneath selected locations. In thisexample, compensated earth surface temperatures will be used to predictthe likelihood of oil or gas deposits beneath locations along the pathof the traverses.

In order to calculate compensated earth surface temperatures for thelocations along the traverses, it was necessary that skywardtemperatures were measured at the same time as the earth surfacetemperatures were measured. The measured skyward temperatures arerecorded in Table I. Skyward temperatures from Traverse 1 are recordedin column "Traverse 1, Sky Temp" and Skyward temperatures from Traverse2 are recorded in column "Traverse 2, Sky Temp."

For this Example, normalized temperature values are used and normalizedcompensated earth surface temperatures are calculated. A normalizedtemperature, as used herein, is the difference between the measuredtemperature value and the average value for the set of measuredtemperatures to which the measured temperature belongs. For example, thenormalized temperature for a skyward temperature measured at a locationon Traverse 1 is the measured skyward temperature at the location minusthe average of all skyward temperatures measured at the locations alongTraverse 1. Normalized temperatures for the other measured temperaturesfrom Traverse 1 and 2 are determined in the same way.

Normalized temperatures have the advantage that, for a measuredtemperature having a value less than the average value of the set towhich it belongs the corresponding normalized temperature has a negativevalue. Likewise, for a measured temperature having a higher than averagevalue, the normalized temperature has a positive value. Thus, by usingnormalized temperature values, it is easy to determine whether aparticular temperature is above or below the average for its set.

The normalized skyward temperatures for Traverse 1 and 2 are recorded inTable I in, respectively, columns labeled "Traverse1, Sky T-Tavg" and"Traverse 2, Sky T-Tavg." Similarly, normalized earth surfacetemperatures for Traverses 1 and 2 are recorded in, respectively,columns labeled "Traverse 1, Earth Surface T-Tavg" and "Traverse 2,Earth Surface T-Tavg" of Table I.

A normalized compensated earth surface temperatures, T_(NCL), iscalculated for each measured earth surface temperature according to theformula:

    T.sub.NCL =T.sub.NL -(C)(T.sub.NS)

Where T_(NCL) is the normalized compensated earth surface temperature;

T_(NL) is the normalized earth surface temperature;

T_(NS) is the normalized skyward temperature at the same location asT_(NL) ; and

C is a constant proportional to the effect that a unit change in thevalue of T_(NS) has upon the value of T_(NL).

For this Example, the value of C, (0.25 degrees per degree), is thevalue which produces the best fit of the calculated values of T_(NCL) ofTraverse 1 and Traverse 2. The value of C was determined by a process ofcurve fitting. That is, a value of C was assumed and a value of T_(NCL)for each measured earth surface temperature of Traverse 1 and Traverse 2was calculated. Curves of T_(NCL) from Traverse 1 and Traverse 2 wereplotted on one graph and the curves were compared. The process wasrepeated with new values of C assumed until the curves for T_(NCL) ofTraverse 1 and 2 showed the best fit with each other.

Values for normalized compensated earth surface temperatures, T_(NCL),for Traverse 1 are recorded in Table 1, column labeled "Traverse 1,Compensated Temp" and are plotted as curve 100 in FIG. 2 of thedrawings. Likewise, the values of T_(NCL) for Traverse 2 are recorded inthe column labeled "Traverse 2, Compensated Temp" and are plotted asCurve 110 in FIG. 2 of the drawings.

Referring to FIG. 1 and 2 of the drawings, it can be seen that thevalues of the normalized earth surface temperatures, T_(NCL), shown incurves 100 and 110 of FIG. 2 show a better correspondence than do thevalues of the measured earth surface temperatures, T_(CL), shown incurves 10 and 11 of FIG. 1. This improved correspondence in values ofT_(NCL) indicates that, by applying the method of the present inventionto the measured earth surface temperatures of Traverse 1 and Traverse 2,much of the effect of variations in skyward temperatures has beenremoved from the earth surface temperature data. Thus, the values ofT_(NCL) for the locations in the geographical area traversed by Traverse1 and 2 may be used to predict whether subsurface features exist beneaththe locations.

In this Example, the geographical area selected, Katy Gas Field, isknown to have gas deposits present. As described above in thisspecification, I have determined that locations having earth surfacetemperatures lower than average for the geographical area are likely tohave oil or gas deposits beneath them, when the geographical area is anarea where such oil or gas deposits might exist. In the same way,locations having normalized compensated earth surface temperatures ofnegative value are likely to have oil or gas deposits beneath them.

In FIG. 2, areas 120 and 130 encompass locations in the geographicalarea having normalized compensated earth surface temperatures, T_(NCL),of negative value. Consequently, according to the present invention,locations within areas 120 and 130 are more likely to have gas depositsbeneath them than are the locations outside the areas 120 and 130.

This example demonstrates that application of methods of the presentinvention to measured earth surface temperature data to compensate forthe effect of variations in skyward temperatures produces compensatedearth surface temperature data, T_(CL) or T_(NCL), for locations withina geographical area which is useful for predicting the presence orabsence of subsurface features beneath the locations. By employing themethods disclosed herein, the required earth surface and skywardtemperature measurements can be made rapidly such that largegeographical areas can be surveyed in a fast, efficient and economicalmanner.

While the present invention has been described with reference topreferred embodiments, the same are to be considered illustrative onlyand not limiting in character, and that many modification to the methodsof the present invention will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention which is definedonly by the appended claims.

                                      TABLE I                                     __________________________________________________________________________    TRAVERSE 1               TRAVERSE 2                                           SKY     EARTH SURFACE                                                                          COMPENSATED                                                                           SKY     EARTH SURFACE                                                                          COMPENSATED                         TEMP.                                                                             T-Tavg                                                                            TEMP.                                                                             T-Tavg                                                                             TEMP    TEMP.                                                                             T-Tavg                                                                            TEMP.                                                                             T-Tavg                                                                             TEMP.                               °F.                                                                        °F.                                                                        °F.                                                                        °F.                                                                         °F.                                                                            °F.                                                                        °F.                                                                        °F.                                                                        °F.                                                                         °F.                          __________________________________________________________________________    -44.26                                                                            0.79                                                                              62.70                                                                             0.19 -0.01   -51.85                                                                            -0.10                                                                             61.80                                                                             0.01 0.04                                -44.36                                                                            0.69                                                                              62.70                                                                             0.19 0.02    -52.05                                                                            -0.31                                                                             61.76                                                                             -0.03                                                                              0.05                                -44.36                                                                            0.69                                                                              62.61                                                                             0.10 -0.07   -52.05                                                                            -0.31                                                                             61.78                                                                             -0.01                                                                              0.07                                -44.36                                                                            0.69                                                                              62.59                                                                             0.08 -0.09   -52.05                                                                            -0.31                                                                             61.76                                                                             -0.03                                                                              0.05                                -44.67                                                                            0.38                                                                              62.59                                                                             0.08 -0.01   -52.05                                                                            -0.31                                                                             61.80                                                                             0.01 0.09                                -44.67                                                                            0.38                                                                              62.59                                                                             0.08 -0.01   -52.05                                                                            -0.31                                                                             61.84                                                                             0.05 0.12                                -44.88                                                                            0.17                                                                              62.56                                                                             0.05 0.00    -51.85                                                                            -0.10                                                                             61.78                                                                             -0.01                                                                              0.02                                -45.29                                                                            -0.24                                                                             62.48                                                                             -0.03                                                                              0.02    -51.85                                                                            -0.10                                                                             61.80                                                                             0.01 0.04                                -45.49                                                                            -0.44                                                                             62.56                                                                             0.05 0.16    -51.64                                                                            0.10                                                                              61.89                                                                             0.10 0.08                                -45.70                                                                            -0.65                                                                             62.52                                                                             0.01 0.17    -51.64                                                                            0.10                                                                              62.05                                                                             0.26 0.24                                -45.90                                                                            -0.85                                                                             62.52                                                                             0.01 0.22    -51.54                                                                            0.20                                                                              62.12                                                                             0.33 0.27                                -45.90                                                                            -0.85                                                                             62.38                                                                             -0.13                                                                              0.08    -51.23                                                                            0.51                                                                              62.16                                                                             0.37 0.24                                -45.90                                                                            -0.85                                                                             62.48                                                                             -0.03                                                                              0.19    -51.03                                                                            0.72                                                                              62.34                                                                             0.55 0.37                                -45.90                                                                            -0.85                                                                             62.56                                                                             0.05 0.26    -50.82                                                                            0.92                                                                              62.39                                                                             0.59 0.36                                -45.90                                                                            -0.85                                                                             62.34                                                                             -0.17                                                                              0.04    -50.51                                                                            1.23                                                                              62.32                                                                             0.53 0.23                                -45.90                                                                            -0.85                                                                             62.21                                                                             -0.30                                                                              -0.08   -50.41                                                                            1.33                                                                              62.30                                                                             0.51 0.18                                -45.70                                                                            -0.65                                                                             62.16                                                                             -0.35                                                                              -0.19   -50.41                                                                            1.33                                                                              62.30                                                                             0.51 0.17                                -45.70                                                                            -0.65                                                                             62.16                                                                             -0.35                                                                              -0.19   -50.21                                                                            1.54                                                                              62.27                                                                             0.48 0.09                                -45.70                                                                            -0.65                                                                             62.12                                                                             -0.39                                                                              -0.22   -50.21                                                                            1.54                                                                              62.16                                                                             0.37 -0.01                               -45.70                                                                            -0.65                                                                             61.87                                                                             -0.64                                                                              -0.48   -50.21                                                                            1.54                                                                              61.78                                                                             -0.01                                                                              -0.39                               -45.70                                                                            -0.65                                                                             62.02                                                                             -0.49                                                                              -0.33   -50.21                                                                            1.54                                                                              61.80                                                                             0.01 -0.37                               -45.70                                                                            -0.65                                                                             62.16                                                                             -0.35                                                                              -0.19   -50.21                                                                            1.54                                                                              61.84                                                                             0.05 -0.34                               -45.70                                                                            -0.65                                                                             62.30                                                                             -0.21                                                                              -0.04   -50.41                                                                            1.33                                                                              62.03                                                                             0.23 -0.10                               -45.49                                                                            -0.44                                                                             62.38                                                                             -0.13                                                                              -0.02   -50.41                                                                            1.33                                                                              61.98                                                                             0.19 -0.14                               -45.70                                                                            -0.65                                                                             62.38                                                                             -0.13                                                                              0.03    -50.41                                                                            1.33                                                                              61.84                                                                             0.05 -0.29                               -45.90                                                                            -0.85                                                                             62.48                                                                             -0.03                                                                              0.19    -50.41                                                                            1.33                                                                              61.89                                                                             0.10 -0.23                               -45.90                                                                            -0.85                                                                             62.45                                                                             -0.06                                                                              0.15    -50.51                                                                            1.23                                                                              61.98                                                                             0.19 -0.12                               -45.90                                                                            -0.85                                                                             62.48                                                                             -0.03                                                                              0.18    -50.62                                                                            1.13                                                                              61.78                                                                             -0.01                                                                              -0.29                               -45.90                                                                            -0.85                                                                             62.32                                                                             -0.19                                                                              0.02    -50.82                                                                            0.92                                                                              61.78                                                                             -0.01                                                                              -0.24                               -45.90                                                                            -0.85                                                                             62.32                                                                             -0.19                                                                              0.02    -51.03                                                                            0.72                                                                              61.73                                                                             -0.06                                                                              -0.24                               -45.70                                                                            -0.65                                                                             62.23                                                                             -0.28                                                                              -0.12   -51.03                                                                            0.72                                                                              61.80                                                                             0.01 -0.17                               -45.70                                                                            -0.65                                                                             62.14                                                                             -0.37                                                                              -0.21   -51.44                                                                            0.31                                                                              61.69                                                                             -0.10                                                                              -0.17                               -45.70                                                                            -0.65                                                                             61.98                                                                             -0.53                                                                              -0.37   -51.64                                                                            0.10                                                                              -61.37                                                                            -0.42                                                                              -0.45                               -45.49                                                                            -0.44                                                                             61.96                                                                             -0.55                                                                              -0.44   -51.85                                                                            -0.10                                                                             61.26                                                                             -0.53                                                                              -0.50                               -45.08                                                                            -0.03                                                                             62.07                                                                             -0.44                                                                              -0.43   -52.05                                                                            -0.31                                                                             61.12                                                                             -0.67                                                                              -0.60                               -44.88                                                                            0.17                                                                              62.16                                                                             -0.35                                                                              -0.39   -52.26                                                                            -0.52                                                                             61.06                                                                             -0.73                                                                              -0.60                               -44.67                                                                            0.38                                                                              62.21                                                                             -0.30                                                                              -0.39   -52.46                                                                            -0.72                                                                             61.17                                                                             -0.62                                                                              -0.44                               -44.36                                                                            0.69                                                                              62.38                                                                             -0.13                                                                              -0.31   -52.46                                                                            -0.72                                                                             61.30                                                                             -0.49                                                                              -0.31                               -44.26                                                                            0.79                                                                              62.48                                                                             -0.03                                                                              -0.23   -52.56                                                                            -0.82                                                                             61.24                                                                             -0.55                                                                              -0.34                               -44.06                                                                            0.99                                                                              62.63                                                                             0.12 -0.13   -52.56                                                                            -0.82                                                                             63.24                                                                             -0.55                                                                              -0.34                               -44.06                                                                            0.99                                                                              62.70                                                                             0.19 -0.06   -52.87                                                                            -1.13                                                                             61.10                                                                             -0.69                                                                              -0.41                               -44.06                                                                            0.99                                                                              62.79                                                                             0.28 0.03    -53.08                                                                            -1.34                                                                             61.26                                                                             -0.53                                                                              -0.20                               -44.06                                                                            0.99                                                                              62.93                                                                             0.41 0.17    -53.08                                                                            -1.34                                                                             61.44                                                                             -0.35                                                                              -0.02                               -44.26                                                                            0.79                                                                              62.99                                                                             0.48 0.28    -53.28                                                                            -1.54                                                                             61.62                                                                             -0.17                                                                              0.21                                -44.26                                                                            0.79                                                                              62.97                                                                             0.46 0.26    -53.59                                                                            -1.85                                                                             61.80                                                                             0.01 0.47                                -44.26                                                                            0.79                                                                              63.02                                                                             0.51 0.32    -53.59                                                                            -1.85                                                                             61.76                                                                             -0.03                                                                              0.44                                -44.26                                                                            0.79                                                                              63.06                                                                             0.55 0.35    -53.28                                                                            -1.54                                                                             61.66                                                                             -0.13                                                                              0.25                                -44.26                                                                            0.79                                                                              63.02                                                                             0.51 0.31    -53.08                                                                            -1.34                                                                             61.76                                                                             -0.03                                                                              0.30                                -44.26                                                                            0.79                                                                              63.02                                                                             0.51 0.31    -52.87                                                                            -1.13                                                                             61.76                                                                             -0.03                                                                              0.25                                -44.36                                                                            0.69                                                                              62.99                                                                             0.48 0.31    -53.08                                                                            -1.34                                                                             61.69                                                                             -0.10                                                                              0.24                                -44.36                                                                            0.69                                                                              62.95                                                                             0.44 0.27    -52.87                                                                            -1.13                                                                             61.78                                                                             -0.01                                                                              0.27                                -44.36                                                                            0.69                                                                              62.97                                                                             0.46 0.29    -52.87                                                                            -1.13                                                                             62.03                                                                             0.23 0.52                                -44.36                                                                            0.69                                                                              63.06                                                                             0.55 0.38    -52.67                                                                            -0.92                                                                             62.16                                                                             0.37 0.60                                -43.85                                                                            1.20                                                                              62.92                                                                             0.41 0.11    -52.67                                                                            -0.92                                                                             62.34                                                                             0.55 0.78                                __________________________________________________________________________

I claim and wish to protect by Letters Patent:
 1. A method forcompensating measured earth surface temperatures for the effects ofskyward temperatures, which method comprises:a). selecting ageographical area of interest upon the earth's surface; b) selecting aplurality of locations within the geographical area of interest; c).measuring an earth surface temperature, T_(L), at each location of aplurality of locations within the geographical area, and simultaneouslymeasuring a skyward temperature, T_(S), in a vertical direction aboveeach location; d). determining an average, T_(SA), of the skywardtemperatures, T_(S), measured at the plurality of locations; e).determining a normalized temperature, T_(NS), for each measured skywardtemperature, T_(S), according to the equation: T_(NS) =T_(SA) -T_(S) ;f). determining, for each location of the plurality of locations, acompensated earth surface temperature, T_(CL), according to the formula:

    T.sub.CL =T.sub.L -(C)(T.sub.NS);

where (C) is a constant proportional to the effect of a variation in themeasured skyward temperature, T_(S), at the respective location upon themeasured earth surface temperature, T_(L).
 2. The method of claim 1,including, a step for calculating the value for constant (C) at anylocation, of the plurality of locations, comprising the substeps of:a).measuring, at a first time, a first earth surface temperature, T_(L-1),and a first skyward temperature, T_(S-1), at the location; b) measuring,at a second time, a second earth surface temperature, T_(L-2), and asecond skyward temperature, T_(S-2), at the location; and c).calculating the value of (C) according to the formula:

    C=(T.sub.L-1 -T.sub.L-2)/(T.sub.S-2 -T.sub.S-1).


3. The method of claim 2, including, calculating the value of (C) foreach location of the plurality of locations.
 4. The method of claim 3,including, selecting a single value of (C), out of all the calculatedvalues of (C), which best fits the calculations of values of T_(CL) forall locations of the plurality of locations.
 5. The method of claim 1,including measuring the earth surface temperatures and the skywardtemperatures for the plurality of locations during a time period duringwhich diurnal changes and weather changes have no substantial effectupon measured earth surface temperatures at the plurality of locations.6. A method for compensating normalized earth surface temperature valuesfor the effects of skyward temperatures, which method comprises:a).selecting a geographical area of interest; b). selecting a plurality oflocations within the geographical area of interest; c) a each locationof the plurality of locations, measuring an earth surface temperature,T_(L), and, simultaneously, measuring a skyward temperature, T_(S),vertically above the location; d). determining an average skywardtemperature, T_(SA), for the skyward temperatures, T_(S), measured atthe plurality of locations; e). determining an average measured earthsurface temperature, T_(LA), for the earth surface temperatures, T_(L),measured at the plurality of locations; f). determining a normalizedskyward temperature, T_(NS), for each measured skyward temperature,T_(S), according to the formula:

    T.sub.NS =T.sub.SA -T.sub.S ;

g) determining a normalized earth surface temperature T_(NL), for eachmeasured earth surface temperature, T_(L), according to the formula:

    T.sub.NL =T.sub.L -T.sub.LA

h). determining for each location of the plurality of locations anormalized compensated earth surface temperature, T_(NCL), according tothe formula:

    T.sub.NCL =T.sub.NL -(C)(T.sub.NS)

here (C) is a constant proportional to the effect of a variation in themeasured skyward temperature, T_(S), upon the measured earth surfacetemperature, T_(L), at the respective location.
 7. The method of claim6, including, a step for calculating the value of constant (C) at anylocation, of the plurality of locations, comprising the steps of:for afirst time, determining a first normalized earth surface temperature,T_(NL-1), and a first normalized skyward temperature, T_(NS-1), for thelocation; for a second time, determining a second normalized earthsurface temperature, T_(NL-2), and a second normalized skywardtemperature, T_(NS-2), for the location; and Calculating the value of(C) according to the formula:

    C=(T.sub.NL-1 -T.sub.NL-2)/(T.sub.NS-2 -T.sub.NS-1)


8. The method of claim 6, including measuring the earth surfacetemperatures and the skyward temperatures for the plurality of locationsduring a time period during which diurnal changes and weather changeshave no substantial effect upon measured earth surface temperatures atthe plurality of locations.